1. Field of the Invention
This invention relates generally to a machine having a hydraulic system and, more particularly, to an industrial truck having a hydraulic system with at least one reservoir for hydraulic fluid and at least one hydraulic pump.
2. Description of the Currently Available Technology
Machines are frequently equipped with a hydraulic system, by means of which, depending on the construction of the machine, various functions of the machine are driven. On industrial trucks, for example, such functions are generally the raising and tilting of a load, the steering of the industrial truck and possibly additional loadhandling functions.
The hydraulic system generally has a reservoir from which hydraulic fluid is sucked by a pump. Installed downstream of the pump is a priority valve which can supply a hydraulic steering device with hydraulic fluid. Hydraulic fluid is also made available to additional hydraulic users by distributor valves that can be actuated as desired. Most of the users in question are hydraulic cylinders, by means of which the forces required to raise, tilt or handle a load are generated. The steering device and the other hydraulic users are also connected to the reservoir by return lines. A descent braking valve to reduce the volume of the flow of hydraulic fluid or a pilot valve to maintain a specified pressure level can be located in corresponding return lines, as necessary.
In known machines, the above mentioned hydraulic components are generally fastened separately from one another to a frame of the machine, and are connected to one another by hoses or pipelines. The known art also discloses that different hydraulic components can be combined into modules and fastened jointly to the frame of the machine. In each case, the known hydraulic systems have a series of discontinuities and connections that are sealed with seals and gaskets of various types to prevent the escape of hydraulic fluid.
Preventing the escape of hydraulic fluid from the hydraulic system is necessary to meet the requirements of occupational health and safety regulations as well as environmental protection regulations. For this purpose, complex and expensive means are employed in the manufacture of the machine to help prevent such hydraulic fluid loss. Nevertheless, during the operation of such hydraulic machines, leaks in the hydraulic system occur repeatedly. These leaks have to be detected and eliminated in the course of service and maintenance operations.
As will be appreciated by one of ordinary skill in the industrial truck art, it would be advantageous to provide a machine of the general type described above in which the danger of the escape of hydraulic fluid can be reduced or eliminated, preferably using simple means.